Manchester United’s struggle to challenge for Champions League qualification has led to £220million being wiped off the club’s stock market valuation in a month.

United, who will be without the injured Wayne Rooney, Robin van Persie and Ashley Young for Sunday’s FA Cup third-round tie against Swansea City at Old Trafford, have seen their share price on the New York Stock Exchange drop by more than 12 per cent from £10.68 to £9.36 since Dec 6 – despite the S&P 500 Index on which the club is listed enjoying a two per cent per cent overall rise in that time.

With the total valuation of the club at £1.75 billion on Dec 6, it had dropped to £1.53 billion during morning trading in New York yesterday.

The drop in the club’s value dates back to early October. Although ­United’s share price rallied in late November, following the announcement of positive forecasts of annual turnover in quarterly accounts, the loss in value since early December has coincided with the team’s inability to break into the top four.

United announced a 29.1 per cent rise in revenues for the first quarter of the year, but while forecasted revenue for the full year was £420-430 million, that figure was based on the assumption that the team would finish at least third in the Premier League this season and reach the Champions League quarter-finals.

With United drawn to face Greek champions Olympiakos in the Champions League round of 16 next month, Moyes’s team appear to be on course to achieve the target of progression to the last eight.

But with Tottenham Hotspur consigning United to their fourth home league defeat of the season on New Year’s Day, the champions lie seventh, five points adrift of fourth-placed Liverpool.

Failure to qualify for next season’s Champions League would mean United missing out on at least £20 million in prize money and potentially damaging their commercial appeal.

United remain determined to add to their squad this month, however, with the club’s owners, the Glazer family, prepared to sanction moves for players identified by Moyes.

Senior figures at United also remain confident that the club can comfortably survive missing out on the Champions League next season, with sizeable funds in place for summer transfer activity.

Despite the growing gap between United and the top four, Moyes insists his team remain capable of climbing the table and challenging in the FA Cup and Capital One Cup, with a semi-final first leg against Sunderland looming on Tuesday.

“I will still keep plugging away and try to win the league games,” Moyes said. “That’s the job. It’s getting that consistency that’s really important. We have yet to find that really, albeit we won six [consecutive games] and had a defeat. I think we had four Premier League wins before the defeat [against Tottenham], but if you are only judging it on results, fine.

“But if you are judging it on performances then it would’ve been a fifth win after how we played.”

Moyes, meanwhile, confirmed that Rooney would miss the Swansea game after having a scan on a groin injury, with Van Persie still sidelined with an injured thigh.

Young will also miss the Swansea game after suffering a shoulder injury following a challenge by Spurs goalkeeper Hugo Lloris on Wednesday.

Young has had a scan and Moyes is hopeful that the injury is just bad bruising.